Hello, I am working on a app with pjsip core library and has ported "simpleua.c" on ios for trial. The "simpleua app" works fine with a service "stateful_proxy.c" on a local server. But if the "stateful_proxy.c" service is at a remote server and talks to the "simpleua app" via 4G, SIP message would lose even with TCP/TLS transport in my testing environment. Then I ported the "pjturn-client.c" on ios and it can exchange data with a remote turn server(coturn) via 4G without problem. Before I start implementing a TURN transport, just want to make sure: do I really need to implement it by myself? Or it is actually enough for SIP messages exchange with UDP/TCP/TLS transport in 4G? Did I miss something? Thanks for your help and answering.